This invention is directed to audio amplifier circuitry, and particular to such circuitry for selectively varying the gain and frequency response in various stages of amplification.
The invention is related to Brown, Sr. et al., U.S. Pat. No. 4,811,401 entitled "Superdistorted Amplifier Circuitry With Normal Gain" and commonly assigned to the assignee herein. The subject matter of the aboveidentified patent is incorporated herein by reference. Brown, Sr. et al. describes an audio frequency amplifier which is selectively operable in a clean (undistorted) mode and a lead (distorted) mode. In the clean mode, a switch completes a ground circuit in the undistorted amplifier stage while the distortion amplifier stage is allowed to float at unity gain and vice versa.
The amplifying circuitry of the aforementioned U.S. patent is used for amplifying musical instruments, particularly electric guitars. Various controls are provided to select the desired mode of operation. The circuitry may be further improved by employing selectable pre and post distortion stage gain and frequency response compensation. In some cases compensation depends upon the mode of operation. For example, i& is desirable to automatically compensate for certain mode changes between clean and lead modes, because without such compensation the musical performance may be adversely affected. Automatic compensation, however necessary, places some limits on the musician's ability to control the available frequency response of the circuitry and hence the ultimate sound. Accordingly, it is desirable to allow the artist to retain a full measure of control in those areas where undesirable effects are unlikely.